This report presents a patient with macrovolt T wave alternans, PVC
with R on T or a long-short sequence followed by torsades de pointes.

Keywords: Macrovolt T wave
Alternans; long QT syndrome

A 35-year-old female was
referred to our hospital due to an episode of syncope in the sitting
position. This episode was preceded by palpitation and happened two
hours prior to our evaluation. There was no history of previous medical
problems or drug usage and her physical examination was completely
normal. Figure 1 illustrates
the 12-lead ECG taken in the emergency room. A few minutes later, she
again briefly lost consciousness and recovered spontaneously. Figure 2 demonstrates the rhythm
strip recorded by cardiac monitoring during this second syncopal
episode.

Figure 2: The beginning of
torsades de pointes after a short coupled PVC on T wave (arrow).

The ECG in Figure 1 shows
normal QRS axis, PR and QRS interval, QTc of 540 msec, and macrovolt T
wave alternans best seen in leads I, aVR and V1 [1,2]. There was no
precipitant for prolongation of QT interval. Macrovolt T-wave alternans
is a harbinger of electrical instability in congenital LQTS, although
it could be seen in acquired LQTS [3]. Figure
2 shows a long QT interval and polymorphic ventricular
tachycardia (torsades de pointes) that began after a long-short
sequence [4]. Two important points regarding this tachyarrhythmia are
it's association with macrovolt T wave alternans in the setting of a
prolong QT interval and its initiation by a long-short sequence or a
PVC during the vulnerable period of the T wave (R on T) [5]. She was
managed by implantation of implantable cardioverter-defirillator (ICD)
and up titration of propranolol to 40 mg three times a day.